[filmscanners] Re: Scene brightness and CCDs

["Anthony Atkielski" <anthony@atkielski.com>]

Austin writes:

> Isn't that a curve issue if you say it's
> only in the mid tones?

It might be, if that were what I had actually said.  But I only mentioned
the midtones; I did not say that only they were affected.

If you divide a 1000000:1 ratio of luminosity into 256 equal parts, the
middle five stops (the midtones) will be divided into only 64 discrete
levels, and will represent only 25% of the total dynamic range.  If you
divide a 1000:1 ratio of luminosity into 256 equal parts, these same
midtones will be divided into 128 levels, or half of all available levels,
and half of the total dynamic range.  If the bulk of your image is recorded
in midtones, as would be typical for most images, properly exposed, the
former gamut will give you only half the tonal resolution and contrast of
the latter.  And if you attempt to improve contrast by boosting the
increments between the midtones with an S curve, you risk posterization in
the first case, but much less so in the second.

This is why wide gamut shows poor contrast in midtones if displayed as-is,
and why it may produce unacceptable results if you simply try to play with
the curves.

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